A wide variety of electronic circuit applications employ differential measurement of two currents and some prescribed amount of rejection of common mode components of the currents. In some applications, the currents being measured may exist in a high DC voltage/current environment, while their information content is ultimately employed in a low voltage/current environment, with demanding requirements for accurate amplification and filtering. As a non-limiting example, various equipment employed by telecommunication service providers utilize subscriber line interface circuits (SLICs) to interface telecommunication signals with phone line wiring that may include substantial DC components.
As another example, fully balanced or differential transimpedance amplifiers may be employed in optical receiver systems, where a current-varying output signal of a photodetector is converted into a voltage signal to be processed by other circuitry. While amplifiers with a balanced load may provide a preferred solution for applications such as those listed above, other considerations such as component count, current dissipation, and the like may result in employment of hybrid circuits.
An amplifier with a balanced differential load may provide significantly improved noise immunity compared to a single-ended amplifier or an amplifier with an unbalanced load such as a current mirror.
Thus, it is with respect to these considerations and others that the present invention has been made.